1. Technical Field
The present invention relates generally to automobile exterior mirror assemblies and more particularly to automobile exterior mirror assemblies comprised of long glass fiber reinforced, UV-stabilized polypropylene materials.
2. Discussion
Automobile exterior mirror assemblies are well-known in the art. One common type of automobile exterior mirror assembly is the side view mirror assembly, which generally allows a driver to observe oncoming automobiles approaching from the rear of the vehicle, either to the left rear side of the vehicle (if one side view mirror is employed) or from both the left and right rear sides of the vehicle (if dual side view mirrors are employed). The deployment and use of such side view mirror assemblies has greatly aided in the safe operation of automobiles.
With reference to FIG. 1, a conventional side view mirror assembly 10 is typically installed on an exterior surface of one or more of the vehicle""s doors 12. With reference to FIGS. 1 and 2, a conventional side view mirror assembly 10 generally include a base plate or cover 14 containing a metallic base chassis 16 which is mounted to the exterior surface of the vehicle""s door 12. A mirror case or housing 18 is pivotably fastened to the base cover 14, allowing the mirror case 18 to move inwardly and outwardly along a horizontal axis relative to the vehicle. A reflective mirror 20 is movably supported within the mirror case 18. The mirror 20 is typically mounted to a mounting plate assembly 22 which allows the mirror 20 to pivot several degrees in several different directions. The mounting plate assembly 22 is typically mounted to a metallic frame 24 secured to the interior surface of the mirror case 18. The metallic frame 24 may also include a portion that functions as a pivot assembly 26.
In modern automobiles, a mirror position adjustment assembly 28 may be provided which allows the mirror 20 to be remotely positioned from inside the vehicle passenger compartment. Typically, a series of cables 30 extend from the back of the mounting plate assembly 22, through various apertures located in the metallic frame 24 and base cover 14, and terminate on a control panel 32 which may include control means 34, such as levers, knobs, toggle switches, and the like, which permit the cables 30 to be manipulated in such a way so as to change the position of the mirror 20.
A more complete discussion of automobile exterior mirror assemblies, including their construction and operation, can be found in U.S. Pat. Nos. 3,370,480; 4,103,560; 4,105,301; 4,167,306; 4,245,893; 4,250,767; 4,251,316; 4,475,414; 4,679,758; 4,740,066; 4,755,033; 4,830,327; 4,836,491; 4,854,539; 4,856,885; 4,867,409; 4,871,953; 4,881,418; Re. 34,142; 4,900,142; 4,904,074; 4,914,972; 4,918,920; 4,919,525; 4,932,766; 5,081,546; 5,166,832; 5,205,182; 5,331,471; 5,355,255; 5,432,640; 5,436,769; 5,563,744; 5,828,504; 5,838,507; 5,841,594; 5,949,596; and 5,971,554, the specifications of all of which are expressly incorporated herein by reference.
Because of increased pressure to reduce automobile construction costs, as well as to increase fuel efficiency, automobile manufacturers have begun to focus on reducing part content and replacing heavy and expensive component materials, such as metallic materials with lighter and less expensive materials, such as thermoplastic materials.
For example, the manufacturers of automobile exterior mirror assemblies have recently started to replace certain metallic components of the mirror assembly, such as the metallic support bracket, as well as the bracket frame and the mirror housing, with polyamide-based materials, such as nylon, or ASA-based materials (acrylic-styrene-acrylonitrile).
Typically, the polyamide is reinforced with various filler materials to provide, among other things, the requisite amount of structural performance, e.g., strength, durability, and the like. One type of common reinforcing material that has been employed are glass fibers, which would typically be present in the amount of about 15 weight percent in filled polyamide-based materials. Although exterior mirror assembly components comprised of filled polyamide-based materials have exhibited adequate strength, durability, and aesthetic appeal, the use of these materials has not achieved the desired cost and weight savings.
ASA-based materials have also proved to be unsatifactory, in that the high gloss levels present on the exterior surfaces of the finished parts have raised aesthetic concerns.
Accordingly, manufacturers have turned their attention to other lighter and less expensive thermoplastic materials, such as polypropylene, especially filled polypropylene.
A general discussion of filled polypropylene materials, including their preparation, can be found by referring to the following U.S. patents:
U.S. Pat. No. 5,514,745, the entire specification of which is expressly incorporated herein by reference, discloses a mixture for melt process moldings, and a molding formed of the mixture. The mixture consists essentially of about 5 to about 70 weight percent of a master batch prepared in the form of pellets formed by cutting a long glass fiber reinforced polypropylene resin, and about 30 to about 90 weight percent of polypropylene resin. The long glass fiber reinforced polypropylene resin is prepared in such a manner that a bundle of continuous reinforcement glass fibers surface-finished with a finishing agent containing a coupling agent is impregnated with a modified polypropylene resin having a functional group capable of chemically bonding with the coupling agent and having a flow rate of about 70 to about 300 grams/10 minutes while the bundle of glass fibers is being drawn. The pellets have a length of about 2 to about 50 millimeters in the direction along the fibers. The glass fibers in the pellets extend uniformly in parallel with each other through a distance substantially equal to the length of the pellets. The pellets have a glass fiber content of about 60 to about 90 weight percent.
U.S. Pat. No. 5,540,986, the entire specification of which is expressly incorporated herein by reference, discloses a stampable sheet made of fiber-reinforced thermoplastic resin whose reinforcement is a glass fiber mat in which a non-oriented fiber layer and a unidirectional fiber layer are mechanically intertwined with each other. In the stampable sheet made of the fiber-reinforced thermoplastic resin, a content of the glass long-fiber bundles forming the unidirectional fiber layer, in the glass fiber mat is 20 weight percent to 80 weight percent, and the glass fiber mat, in which a significant amount of glass long-fiber bundles among the glass long-fiber bundles forming the unidirectional fiber layer or a significant amount of glass long-fibers in the glass long-fiber bundles forming the unidirectional fiber layer is substantially under a relaxation condition, is used in an amount of 20 weight percent to 55 weight percent.
U.S. Pat. No. 5,660,770, the entire specification of which is expressly incorporated herein by reference, discloses a process which includes comminuting a first thermoplastic material, e.g., polypropylene, reinforced with short glass fiber (10-40 micrometers). One hundred parts by weight of the comminuted material are mixed with 11-43 parts by weight of chips of a second thermoplastic material, which is reinforced with long glass fiber (about 10-20 millimeters). The melts of the two thermoplastic materials should be mutually mixable. The mixture is subjected to thermoplastic forming.
Recent attempts to manufacture exterior mirror assembly components with filled polypropylene have generally produced unsatisfactory results. Although the use of short glass fiber filled polypropylene allowed manufacturers to reduce costs and weight to a certain extent, several significant problems were identified. First, the use of glass fibers at too low of a weight percent has resulted in structural performance concerns, such as impaired strength and impact resistance. Conversely, the use of glass fibers at too high of a weight percent has resulted in aesthetic appearance concerns, such as surface irregularities caused by protruding glass fibers.
Therefore, there exists a need for automobile exterior side view mirror assembly components comprised of filled polypropylene materials, wherein the components exhibit outstanding physical performance characteristics, are aesthetically pleasing, and are easily and inexpensively manufactured.
In accordance with one embodiment of the present invention, an automotive exterior mirror assembly component is provided, wherein the component is comprised of a mixture of polypropylene and long glass fibers.
In accordance with another embodiment of the present invention, an automotive exterior mirror case component is provided, wherein the component is comprised of a mixture of polypropylene and long glass fibers.
In accordance with still another embodiment of the present invention, an automotive exterior base plate component is provided, wherein the component is comprised of a mixture of polypropylene and long glass fibers.
In accordance with yet another embodiment of the present invention, an automotive exterior integral mirror case/frame component is provided, wherein the component is comprised of a mixture of polypropylene and long glass fibers.
In accordance with still yet another embodiment of the present invention, an automotive exterior integral base plate/base chassis component is provided, wherein the component is comprised of a mixture of polypropylene and long glass fibers.
In accordance with a further embodiment of the present invention, a method for making an automotive exterior mirror assembly component is provided, comprising:
providing a mixture of polypropylene and long glass fibers;
heating the mixture above its glass transition temperature;
injecting the heated mixture into a cavity of a mold, wherein the cavity has a configuration substantially identical to the component; and
removing the component from the cavity of the mold.
A more complete appreciation of the present invention and its scope can be obtained from understanding the accompanying drawings, which are briefly summarized below, the following detailed description of the invention, and the appended claims.